Field of the Invention
The present disclosure relates to a transformable device and a method of manufacturing the transformable device. More, particularly, the present disclosure relates to a transformable device including electrodes therein, and a method of manufacturing the transformable device.
Description of the Related Art
An electro-active polymer (EAP) is a polymer which is transformable by electrical stimulation, and means a polymer which can be repeatedly expanded, contracted, and bent by electrical stimulation. Among various kinds of electro-active polymers, a ferroelectric polymer and a dielectric elastomer are mainly used. For example, the ferroelectric polymer includes PVDF (Poly VinyliDene Fluoride) and P(VDF)-TrFE (Poly(VinyliDene Fluoride)-trifluoroethylene), and the dielectric elastomer may be based on silicon, urethane, acryl, or the like.
The ferroelectric polymer has advantages of satisfactory flexibility and satisfactory permittivity, but has a significant problem in optical properties such as light transmissivity. Thus, it is difficult to use the ferroelectric polymer on the whole face of a display device. Meanwhile, the dielectric elastomer has satisfactory transmissivity, but a driving voltage thereof is high. Thus, there is a problem that it is difficult to use, as it is, the dielectric elastomer in a display device with a relatively low driving voltage such as a mobile device.
However, the dielectric elastomer of the electro-active polymers generally has flexibility and elasticity by which a shape thereof is variously transformable. Accordingly, fields in which dielectric elastomers can be utilized has been recently studied with a flexible display device which has been actively developed. For convenience of description, hereinafter, it is assumed that the dielectric elastomer is used as the electro-active polymer.
When an electric field is applied to an electro-active layer through electrodes disposed on both of an upper face and a lower face of the electro-active layer consisting of electro-active polymers, polarization occurs inside the electro-active layer. Positive charges and negative charges are accumulated on the electrodes disposed at an upper portion and a lower portion of the electro-active layer due to such polarization, respectively, and Maxwell Stress is applied to the electro-active layer by electrostatic attractive force (coulombic force) generated among the accumulated charges. A formula representing a magnitude of Maxwell Stress is as follows.
                              Maxwell          ⁢                                          ⁢                      Stress            ⁡                          (              P              )                                      =                                            ɛ              r                        ⁢                          ɛ              o                        ⁢                          E              2                                =                                    ɛ              r                        ⁢                                                            ɛ                  o                                ⁡                                  (                                      V                    t                                    )                                            2                                                          [                  Math          ⁢                                          ⁢          1                ]            
Herein, Maxwell Stress means force of an electro-active layer to be contracted in a thickness direction and to be expanded in a length direction by electrostatic attractive force of charges. Due to a property of an electro-active layer transformed by Maxwell Stress, the electro-active layer is in the limelight as a new material constituting an electro-active layer of a transformable device.
Referring to Math 1, the magnitude P of Maxwell Stress is proportional to magnitudes of permittivity ∈r, electric field E, and voltage V of the electro-active layer. When the magnitude of Maxwell Stress gets larger, the electro-active layer has more displacement or is further transformed. Accordingly, in order to increase the displacement or the degree of transformation of the transformable device, the magnitude of Maxwell Stress has to be increased. Thus, in order to increase Maxwell Stress and lower the driving voltage of the transformable device, a study to raise permittivity of the electro-active layer or to raise an effective electric field is being conducted.
By flexibility and elasticity of the electro-active layer and Maxwell Stress, a method of disposing and forming electrodes in a transformable device rises as an important matter. An electrode formed by sputtering that is a general electrode forming method may be damaged by transformation at the time of operating a transformable device including an electro-active layer consisting of electro-active polymers, and performance of the transformable device is decreased in accordance with repeated operating of the transformable device. An electro-active polymer layer may be inserted between support substrates on which electrodes are formed by the other method. However, since the support substrates have unsatisfactory flexibility as compared with the electro-active layer, the displacement of the electro-active layer may be restricted by the support substrates. Therefore, as an electrode applied to a transformable device including an electro-active layer consisting of electro-active polymers, a soft electrode suitable for transformation is used.
As such a soft electrode, an electrode manufactured by mixing an elastic body with carbon conductive grease, carbon black, or carbon nanotube (CNT) was used. Such an electrode may be formed by a printing process, and has problem that a sheet resistance property is not satisfactory and a process is not easy.
Thus, a transformable device and a method of manufacturing the transformable device are necessary, of which performance is not decreased in spite of repeated operating, displacement of an electro-active layer can be maximally secured by Maxwell Stress, and a manufacturing process is easy.
In order to solve the problem of low performance and shortened life of the electrodes of the transformable device as described above, the inventors of the present disclosure have invented a new-structure transformable device and a method of manufacturing the same with electrodes formed inside an electro-active layer.
An object of the present disclosure is to provide a transformable device and a method of manufacturing the same being able to form electrodes inside an electro-active layer by a simple process.
Further, another object of the present disclosure is to provide a transformable device and a method of manufacturing the same capable of keeping performance of an electrode in spite of repeated operating and increasing a life in accordance with forming an electrode inside the electro-active layer.
Further, still another object of the present disclosure is to provide a display device which does not require a separate adhesive layer used to adhere an electrode outside a transformable device and a separate shielding layer in accordance with forming an electrode inside the transformable device and which is thereby thin.
Objects of the present disclosure are not limited to the objects described above, and other objects which are not mentioned above can be clearly understood by a person skilled in the art from the following description.